docs: library comments say what the scanner and resolver do, not how they came to be (#6277)

Rewrites the internal/library comment blocks to rule 32. Task, milestone,
decision and rule ids are gone; the incidents behind them are restated as
the constraint they left (why a file is deleted before its row, why the
missing mark is a mark, why duplicates block on duration). Counts and
album names from one library are dropped from production comments; test
comments keep the names their fixtures use. The tagReadVersion log keeps
each version's before and after, without the measurements.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/library/fingerprint_backfill.go

@@ -13,11 +13,11 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
-// Fingerprint backfill (M400 #3908).
+// Fingerprint backfill.
 //
-// The scan fingerprints only bytes it has not seen (see scanFile), so every track
-// imported before fingerprinting existed — and every row derived by an older
-// fingerprintVersion — needs a pass of its own. That pass is this worker.
+// The scan fingerprints only bytes it has not seen (see scanFile), so every
+// track imported before fingerprinting existed — and every row derived by an
+// older fingerprintVersion — needs a pass of its own. That pass is this worker.
 //
 // Its own worker rather than a stage in RunScan, for two reasons, both about
 // time:
@@ -28,20 +28,23 @@ import (
 //   - A long stage holds the scan run in flight, and a manual rescan answers 409
 //     for as long as it runs.
 //
-// Progress is read live (FingerprintCoverage, the admin gauge) rather than from a
-// scan_runs tally: the work spans many passes with no single run to attach to.
+// Progress is read live (FingerprintCoverage, the admin gauge) rather than from
+// a scan_runs tally: the work spans many passes with no single run to attach
+// to.
 
 // fingerprintBackfillTick is how often the worker looks for work. Once the
-// library has caught up, a tick is one indexed query; mostly the hour bounds how
-// long a file that timed out on a slow mount waits before it is tried again.
+// library has caught up, a tick is one indexed query; mostly the hour bounds
+// how long a file that timed out on a slow mount waits before it is tried
+// again.
 const fingerprintBackfillTick = time.Hour
 
-// fingerprintBackfillBatch is how many tracks one query hands the worker. Small,
-// so tracks the scan adds mid-pass are not stuck behind one enormous page.
+// fingerprintBackfillBatch is how many tracks one query hands the worker.
+// Small, so tracks the scan adds mid-pass are not stuck behind one enormous
+// page.
 const fingerprintBackfillBatch = 50
 
-// fingerprintBackfillConcurrency is the shipped value of the concurrency setting
-// (#3913): how many files are decoded at once. Two is deliberately low: fpcalc
+// fingerprintBackfillConcurrency is the shipped value of the concurrency
+// setting: how many files are decoded at once. Two is deliberately low: fpcalc
 // and the stream hash compete with playback transcoding for CPU and with
 // streaming for the mount, and a backfill that makes playback stutter is worse
 // than one that takes longer.
@@ -75,7 +78,8 @@ type FingerprintBackfillWorker struct {
 	tick     time.Duration
 	batch    int32
 	// fingerprint is a field for the same reason as Scanner.fingerprint: an
-	// integration test pins which tracks a pass touches, not what the tools print.
+	// integration test pins which tracks a pass touches, not what the tools
+	// print.
 	fingerprint func(ctx context.Context, path string, opts fingerprintOptions) fingerprintResult
 }
 
@@ -110,8 +114,8 @@ func (w *FingerprintBackfillWorker) Run(ctx context.Context) {
 	}
 }
 
-// runOnce contains a pass so that nothing it does — an error, a panic — can stop
-// the next tick from firing (rule 157).
+// runOnce contains a pass so that nothing it does — an error, a panic — can
+// stop the next tick from firing.
 func (w *FingerprintBackfillWorker) runOnce(ctx context.Context) {
 	defer func() {
 		if r := recover(); r != nil {
@@ -135,10 +139,10 @@ func (w *FingerprintBackfillWorker) runOnce(ctx context.Context) {
 // retried forever within the pass.
 //
 // Settings are read before every batch, so a save takes effect within a batch
-// rather than an hour (#3913): switching fingerprinting off ends the pass, a new
-// concurrency applies to the next batch, and a new length restarts the walk from
-// the top at that length, because every row written at the old one went stale
-// the moment it changed.
+// rather than an hour: switching fingerprinting off ends the pass, a new
+// concurrency applies to the next batch, and a new length restarts the walk
+// from the top at that length, because every row written at the old one went
+// stale the moment it changed.
 func (w *FingerprintBackfillWorker) pass(ctx context.Context) (BackfillFingerprintsResult, error) {
 	q := dbq.New(w.pool)
 	var (
@@ -146,7 +150,8 @@ func (w *FingerprintBackfillWorker) pass(ctx context.Context) (BackfillFingerpri
 		mu  sync.Mutex
 	)
 	// The all-zero uuid sorts before every real id. Valid must be true: a NULL
-	// cursor would make "id > NULL" match nothing and every pass a silent no-op.
+	// cursor would make "id > NULL" match nothing and every pass a silent
+	// no-op.
 	start := pgtype.UUID{Valid: true}
 	after := start
 	lengthSec := w.settings.Get().ChromaprintLengthSec